Horizontal axis wind turbine

ABSTRACT

A horizontal axis wind turbine is disclosed. When a wind direction changes to blow against a rotor from a rear side, a pitch angle of a rotor blade of the rotor are controlled to reverse a rotation of the rotor, without turning of the rotor to the rear side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2005-011225, filed on Jan. 19, 2005, and the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a horizontal axis wind turbine, and more particularly to a horizontal axis wind turbine in which a rotating direction of a rotor changes according to a change of the wind direction by, for example, changing pitch angles of rotor blades, and further the direction of the wind turbine can be changed appropriately according to the change of the wind direction at its placed position.

2. Description of the Related Art

There has been known a horizontal axis wind turbine of downwind type, for example, as shown in FIG. 5, as a conventional example of a horizontal axis wind turbine which performs direction control according to a change of the wind direction (the following Patent Document 1). In the direction control of such a horizontal axis wind turbine, a rotor of the wind turbine is so controlled to face perpendicularly to or closely perpendicularly to a wind direction which has an azimuth angle of the wind turbine (or a displacement angle in a horizontal plane of a rotor shaft of the wind turbine) and a tilt angle of the wind turbine (or a displacement angle of a rotor shaft in a plane perpendicular to the above-described horizontal plane). This horizontal axis wind turbine utilizes a characteristic that an upflow angle or a downflow angle of a wind depends on the lay of the land. Specifically, when a wind direction toward a wind turbine 100 is, in a direction with a certain azimuth angle, one as indicated by an arrow Q in FIG. 5 having an angle of α to the horizontal plane, a nacelle 102 rotates on each of an inner cam track 104 and an outer cam track 105 so that a rotor shaft 103 a of a rotor 103 turns to point to a certain azimuth angle of the wind direction and stops. At a stop position, a tilt angle, that is a wind-direction angle to the horizontal plane) is set to α, corresponding to the certain azimuth angle. Accordingly, the inclination angle of the rotor shaft 103 a with respect to the upper surface of a tower head pedestal 101 a in a plane parallel to the horizontal plane comes to be α. As a result, the wind turbine 100 comes to be a state that the rotor 103 faces perpendicularly to the flow of wind in the wind direction. Further, in FIG. 6 for example, when a wind direction toward the wind turbine 100 changes from an original wind direction (shown by solid lines) indicated by an arrow R in the figure to a wind direction (shown by dotted lines) indicated by an arrow S, the nacelle 102 changes its direction corresponding to the wind direction indicated by the arrow R so that the rotor shaft 103 a turns to the flow direction of this azimuth angle and stops (at the stop position, a wind direction angle in the tilt angle direction is set to zero corresponding to the wind direction of this azimuth angle), and the wind turbine 100 comes to the state that the rotor 103 faces perpendicularly to the direction of the wind flow. When the wind direction changes to the direction indicated by the arrow S, the nacelle 102 rotates on the inner cam track 104 and the outer cam track 105 by 180 degrees so that the rotor 103 faces the wind flow in this azimuth angle and stops (at the stop position, a wind direction angle in the tilt angle direction is set to β corresponding to the wind direction of the azimuth angle). At this time, the wind turbine 100 becomes to a state that the rotor 103 faces perpendicularly to the flow of wind in the wind direction. Here, numeral 106 denotes a roller attached to the nacelle 102.

The horizontal axis wind turbine described above is so constructed that the nacelle moves to turn by 180 degrees when a wind flow in a direction of a certain azimuth angle changes to a wind flow in the opposite direction, and as to the displacement in a tilt angle direction corresponding to a wind direction in a certain azimuth angle direction, the cam tracks are provided with surfaces formed in advance so that the value of a tilt angle differs according to the azimuth angle. According to such a structure, the cam tracks have to be produced having different values of tilt angles correlative to azimuth angles for every installing position, and further a difficulty occurs in work for correcting the angle once set.

[Patent Document 1] JP-2003-35249A (pages 2-4, and FIGS. 3 and 4).

SUMMARY OF THE INVENTION

An object of the invention is to provide a horizontal axis wind turbine that is not complicated in installation work and relatively flexible in correction after installation with respect to controlling an azimuth angle and a tilt angle according to a change of wind direction.

According to the first aspect of the invention, in the horizontal axis wind turbine, when a wind direction changes to blow against a rotor from a rear side, a pitch angle of a rotor blade of the rotor are controlled to reverse a rotation of the rotor, without turning of the rotor to the rear side.

Accordingly, because the change of pitch angle of the blades and the reverse in the rotating direction of the rotor can be performed without turning movement of a nacelle which was required by the above-described conventional example, installation work is not complicated due to omission of work for rotating the nacelle, and correction after installation becomes easier. As a result, the cost for maintenance can be cut down.

Preferably, the horizontal axis wind turbine comprises: a nacelle to support the rotor; a tower head which the nacelle is mounted on and comprises a rail with a circular or arc shape thereon; and a roller to support the nacelle, which is movable on and guided by the rail, to control an azimuth direction of the wind turbine. In the horizontal axis wind turbine, each roller is moved on the rail with a circular or arc shape, in a limited range to correspond to the change of wind direction in the range, which allows the wind turbine to be adjusted within a narrow range for the wind direction in the azimuth-angle direction.

Preferably, the horizontal axis wind turbine further comprises an extendable and retractable actuator with which the rail is supported on the tower head, to control an inclination angle of the wind turbine so as to coincide with an upflow or downflow angle of a wind.

According to such a horizontal axis wind turbine, the inclination angle can be controlled by extending and retracting the actuators without producing a special cam track which was required by the above-described conventional example, therefore installation cost can be reduced including omission of work to lift a large cam, and further a horizontal axis wind turbine more precisely facing the wind direction can be implemented.

In accordance with the second aspect of the invention, the horizontal axis wind turbine comprises: a rotor having a rotor blade; a nacelle to support a rotary shaft of the rotor; a tower head which the nacelle is mounted on and comprises a rail with a circular shape thereon supported by an extendable and retractable actuator; and a roller rotatably attached to the nacelle through a shaft, wherein the roller is movable to rotate on and guided by the rail, to coincide an azimuth direction of the wind turbine with the azimuth direction of a wind, and the actuator is extendable and retractable to make an inclination angle of the wind turbine coincide with an upflow or downflow angle of the wind.

According to such a horizontal axis wind turbine, in addition to the omission of work to lift the large cam, since the rotating shaft of the rotor can precisely follow the change of wind direction without being fixed to a direction, the wind turbine needs not to be repaired even when some changes are necessitated after the installation.

The horizontal axis wind turbine may be a downwind type.

Preferably, the rotor comprises a plurality of rotor blades, and a pitch angle of each of the rotor blades is independently changeable to each other.

The pitch angle of a rotor blade is preferably changed by rotating the rotor blade about a pitch axis thereof.

The rotation of the rotor blade about the pitch axis may be performed by rotating a base end of the rotor blade by a motor provided in a hub, through a gear.

Preferably, the actuator is a hydraulic jack.

The horizontal axis wind turbine according to the invention allows the pitch angle of blades to be changed and the rotating direction of the rotor to be reversed when the wind turbine is fixed at a place where the wind direction is almost constant as for the seasons, or as in a coast side or a mountain side where a wind from the sea or an upflow wind blows in the daytime and a land wind or a downflow wind blows at night. Further, when the wind turbine is installed at a place where wind directions are changeable, in addition to the above-described changes of the pitch angle and the reverse of rotation, the wind turbine follows the azimuth direction of a wind using the rails and the rollers rotatably moving thereon, and controls the inclination angle by up-and-down control of the actuators to coincide with the wind direction. Accordingly, the wind turbine of the invention has advantages in that installation can be relatively easier and the change after the installation can be also easier.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawing which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein;

FIG. 1 is a perspective view showing a horizontal axis wind turbine according to a first embodiment of the present invention;

FIG. 2 is a view for illustrating the operation of the horizontal axis wind turbine;

FIG. 3A is a view for illustrating the operation of a horizontal axis wind turbine according to a second embodiment of the invention, and FIG. 3B is a partially sectional view taken along the line A-A in FIG. 3A;

FIG. 4 is a view for illustrating the operation of the horizontal axis wind turbine according to the second embodiment of the invention;

FIG. 5 is a view for illustrating the operation of a conventional horizontal axis wind turbine; and

FIG. 6 is a view for illustrating the operation of the conventional horizontal axis wind turbine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A horizontal axis wind turbine according to a first embodiment of the invention will be explained with reference to FIGS. 1 and 2. The wind turbine will be explained by using a downwind horizontal axis wind turbine 1 as shown in FIG. 2.

Such a horizontal axis wind turbine 1 includes a tower 2 placed on the ground, an approximately cylindrical nacelle 4 directly fixed to the tower 2, a rotor shaft (not shown) rotatably supported to the nacelle 4, a hub 6 a fixed to the rotor shaft, and a rotor 6 having three blades 6 b 1-6 b 3 in the embodiment, each blade attached to the hub 6 a so that its pitch angle is changeable. Each of the blades 6 b 1-6 b 3 is attached to the hub 6 a so as to be perpendicular to the rotor shaft.

Regarding the change of the pitch angle in the horizontal axis wind turbine 1, each pitch angle of the blades 6 b 1-6 b 3 is independently changeable, though not shown particularly. For the blade 6 b 1, for example, the base end thereof is attached to a ring gear which is rotatably supported to the hub 6 a through a bearing. The ring gear engages with a pinion which is driven by a motor fixed to the inside of the hub 6 a. Thus, the blade is turned about a pitch axis X, so that the pitch angle of the blade 6 b 1 can be changed.

The control operation of the horizontal axis wind turbine 1 will be explained with reference to FIG. 2.

As described above, when the wind turbine 1 is placed on the lay of the land like coastline, it is required to control mainly the azimuth angle because wind directions are relatively stable such that a wind blows from the sea to the land in the daytime and from the land to the sea at night, and blows along the ground. For example, when a wind blows in the direction indicated by the arrow K in the figure in the daytime, the rotor 6 of the wind turbine 1 rotates with a rotating surface facing perpendicular to the flowing direction of the wind, and each of the blades 6 b 1-6 b 3 of the rotor 6 is controlled to have a predetermined pitch angle as described above. On the contrary, when the wind direction changes in a direction reverse to the arrow K at night, the wind turbine 1 changes the pitch angle of each of the blades 6 b 1-6 b 3 corresponding to the change of wind direction, to reverse the rotating direction of the rotor 6. Accordingly, the wind turbine 1 can correspond to the change of wind direction with change of the pitch angle of the blades 6 b 1-6 b 3 and with reverse of the rotating direction of the rotor 6 without rotational movement of the nacelle 4. Accordingly, the placement work for the wind turbine is not troublesome, and correction thereof after the placement can be performed easily and the cost therefor can be cut down.

Next, a horizontal axis wind turbine according to a second embodiment of the invention will be explained with reference to FIGS. 3A, 3B and 4. Here, the elements in FIGS. 3A, 3B and 4 which are substantially the same as corresponding elements in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof is omitted.

A horizontal axis wind turbine 20 is a downwind horizontal axis wind turbine similar to the above-described wind turbine 1. However, the wind turbine 20 can control azimuth angles and tilt angles according to the change of wind direction which is indicated by an arrow in FIG. 3A.

The horizontal axis wind turbine 20 includes, as shown in FIG. 3A, a tower head pedestal 3 arranged on the above-described tower 2 which is placed on the ground, and a nacelle support member 8 on which the nacelle 4 is disposed to be rotatable about a vertical axis above the pedestal 3 through a bearing 7. The support member 8 supports the nacelle 4 by a pin 9 disposed at the center lower part of the nacelle 4 so that the nacelle 4 can be swung in a direction perpendicular to the pedestal 3. Here, in the bearing 7, the inner ring side is mounted on the nacelle support member 8, and the outer ring is mounted on the pedestal 3.

The wind turbine 20 can be adjusted within a limited range for a wind in the azimuth-angle direction. Specifically, as shown in FIG. 3B, there are provided at the lower part of the nacelle 4 with a motor 10 and a gear 11 driven by the motor 10. The gear 11 rotates integrally with a roller 12 which is attached to a shaft fixed to the lower part of the nacelle 4. The rollers 12 are controlled to move on a plurality of rails 13 which are arranged in an arc-shape on the pedestal 3. In this embodiment, three arc-shaped rails 13 are provided. This allows the wind turbine 20 to be adjusted within a limited range for a wind direction in the azimuth-angle direction. Here, the arc-shaped rails 13 are not disposed directly on the pedestal 3 but are disposed on hydraulic jacks (actuators) 14 which can extend and retract in an up-and-down direction on the pedestal 3, which will be explained later.

Further, the horizontal axis wind turbine 20 has a structure which is compliant with a change of the wind direction in the tilt-angle direction. Specifically, a hydraulic jack 14 which is arranged between the pedestal 3 and each of the arc-shaped rails 13, as described above. The hydraulic jacks are controlled to extend or retract in the up-and-down direction so that the tilt angle of the rotor 6 changes in synchronism with the azimuth angle of the rotor 6 due to the wind direction. Such displacement of the tilt angle may be interlocked with the azimuth angle by setting in advance the correlation between a tilt angle and an azimuth-angle of wind direction, or may be determined such that, by measuring in advance the upflow angle or the downflow angle and the inclination angle of the rotor shaft, oil supply to the jacks may be stopped when both of the angles come into coincidence with each other.

The control operation of the horizontal axis wind turbine 20 will be explained with reference to FIGS. 3A and 3B.

When, for example, a wind blows in a direction indicated by an arrow L in the FIG. 3A in the daytime, the rotor 6 of the wind turbine 20 rotates with its rotating plane facing perpendicular to the flow of the wind direction, and each of the blades 6 b 1-6 b 3 is controlled to have a predetermined pitch angle as described above. However, when the wind direction changes to a direction reverse to the arrow L at night, the pitch angle of each of the blades 6 b 1-6 b 3 is changed corresponding to the change of wind direction to reverse the rotating direction of the rotor 6. When a limited range of adjustment is required for a wind direction in the azimuth-angle direction, the wind turbine 20 is controlled to drive the rollers 12 by the motor 10, to move along the arc-shaped rails 13 by a predetermined amount.

When the horizontal axis wind turbine 20 is placed on the lay of the land like a mountain side, a tilt angle and if needed, an azimuth angle are controlled, because a wind blows in the upper direction along the ground in the daytime, and blows in the lower direction at night. The control operation of the wind turbine 20 in such a case will be explained with reference to FIG. 4.

When a wind blows, in a direction with a certain azimuth angle, for example, as indicated by an arrow M in the Figure in the daytime, having an angle of “x” to the horizontal plane, the rotor 6 of the wind turbine 20 rotates with its rotating plane facing perpendicular to the flow of the wind direction, and each of the blades 6 b 1-6 b 3 is controlled to have a predetermined pitch angle as described above. Since a wind-direction angle in the tilt-angle direction is set to “x” corresponding to the wind direction in such an azimuth angle, the hydraulic jacks 14 are controlled to move in the up-and-down direction so that the rotor shaft has an inclination angle of “x” on the plane perpendicular to the pedestal 3. At this time, the wind turbine 20 is in a state that the rotation plane of the rotor 6 is perpendicular to the flow of the wind direction. On the contrary, when the wind direction changes at night to one in a certain azimuth-angle direction, as indicated by an arrow N of the rear side, having an angle of “y” influenced by the lay of the land where the tower 2 is placed (as shown by broken lines), the pitch angle of each of the blades 6 b 1-6 b 3 is changed to correspond to the wind direction changed, to reverse the rotating direction of the rotor 6. Further, since a wind-direction angle in the tilt-angle direction is set to “y” to correspond to the wind direction in such an azimuth angle, the hydraulic jacks 14 are controlled to move in the up-and-down direction so that the rotor shaft has an inclination angle of “y” in the plane perpendicular to the pedestal 3. At this time, the wind turbine 20 is in a state that the rotational plane of the rotor 6 is perpendicular to the flow of the wind direction. If a limited range of adjustment is required for a wind in the azimuth-angle direction, the wind turbine 20, as described above, is controlled to drive the rollers 12 by the motor 10, to move along the arc-shaped rails 13 by a predetermined amount.

The horizontal axis wind turbine of the invention placed in a coast side or a mountain side can control its azimuth angle and tilt angle according to the particular situation, by selecting the control of azimuth angles and tilt angles according to the change of wind direction due to the seasons or the day and night. It enables reducing difficulties in placement of horizontal axis wind turbines and cutting down a building cost relative to electric power generation by effectively utilizing the wind. Accordingly, the invention has high utility value in such places that have lots of coastlines and mountainous regions as in Japan. 

1. A horizontal axis wind turbine, wherein when a wind direction changes to blow against a rotor from a rear side, a pitch angle of a rotor blade of the rotor are controlled to reverse a rotation of the rotor, without turning of the rotor to the rear side.
 2. The horizontal axis wind turbine according to claim 1, comprising: a nacelle to support the rotor; a tower head which the nacelle is mounted on and comprises a rail with a circular or arc shape thereon; and a roller to support the nacelle, which is movable on and guided by the rail, to control an azimuth direction of the wind turbine.
 3. The horizontal axis wind turbine according to claim 2, further comprising an extendable and retractable actuator through which the rail is supported on the tower head, to control an inclination angle of the wind turbine so as to coincide with an upflow or downflow angle of a wind.
 4. The horizontal axis wind turbine comprising: a rotor having a rotor blade; a nacelle to support a rotary shaft of the rotor; a tower head which the nacelle is mounted on and comprises a rail with a circular shape thereon supported by an extendable and retractable actuator; and a roller rotatably attached to the nacelle through a shaft, wherein the roller is movable to rotate on and guided by the rail, to make an azimuth direction of the wind turbine coincide with the azimuth direction of a wind, and the actuator is extendable and retractable to make an inclination angle of the wind turbine coincide with an upflow or downflow angle of the wind.
 5. The horizontal axis wind turbine according to claim 1, wherein the horizontal axis wind turbine is a downwind type.
 6. The horizontal axis wind turbine according to claim 1, wherein the rotor comprises a plurality of rotor blades, and a pitch angle of each of the rotor blades is independently changeable to each other.
 7. The horizontal axis wind turbine according to claim 6, wherein the pitch angle of a rotor blade is changed by rotating the rotor blade about a pitch axis thereof.
 8. The horizontal axis wind turbine according to claim 7, wherein rotation of the rotor blade about the pitch axis is performed by rotating a base end of the rotor blade by a motor provided in a hub, through a gear.
 9. The horizontal axis wind turbine according to claim 3, wherein the actuator is a hydraulic jack. 